A generally known pulse wave sensor device includes a light emitter that irradiates a finger with light and a light receiver that receives light reflected by the finger, and detects a pulse wave based on a change in quantity of light between the light emitted from the light emitter and the light received by the light receiver (for example, see Patent Documents 1 to 3).
When a finger is strongly pressed to the light emitter or the light receiver, the finger is compressed and blood flow in arteries is blocked. Hence, a pulse wave signal becomes weak and the pulse wave is no longer detected. With regard to this, Patent Document 1 discloses a configuration in which pressing force detecting means for detecting a pressing force of a finger is provided, and a function of informing a user if the pressing force is strong is added.
Also, Patent Documents 2 and 3 disclose a configuration in which a light emitter is provided to protrude with respect to the periphery of the light emitter to allow the light emitter to reliably contact a finger, so that a pulse wave can be easily detected.
Patent Document 1: International Publication No. 94/015525
Patent Document 2: Japanese Unexamined Patent Application Publication No. 2004-000467
Patent Document 3: Japanese Unexamined Patent Application Publication No. 2008-048987
The pulse wave sensor device in Patent Document 1 has the function of informing the user about that measurement cannot be performed because the pressing force of the finger is too strong. However, with this configuration, even when the pressing force of the finger is strong and measurement cannot be performed, only the information is only provided. Owing to this, to perform measurement for a certain time, the pressing force of the finger has to be held stably in a weak state, and thus the user is forced to bear the burden.
Also, Patent Documents 2 and 3 disclose the configuration in which the light emitter is provided to protrude with respect to the periphery of the light emitter to allow the light emitter to reliably contact the finger. However, the configuration does not reduce the pressing force of the finger, the situation, in which the pulse wave cannot be detected if the pressing force of the finger is too strong, is not changed, and hence a problem similar to the above-described problem arises.